A typical rotary joint is an electro-mechanical device that provides the required signal transfer interface between the stationary and rotating sections of a rotating antenna system. It allows radio-frequency (RF) signals to be transmitted back and/or forth between the antenna and other components of an antenna apparatus.
RF rotary joints are used in many industries. These industries include communication, satellites, aerospace and air traffic control, airborne systems, shipboard systems, ground based radar.
A rotary joint is a passive rotating transmission line that has the ability to pass RF signals with minimal degradation. However, the more RF channels required to be transmitted, generally the longer must be the rotary joint. A rotary joint can be as simple as a one-channel transmission device which is typically small (several cm in length), or as complicated as, say, a transmission device for transmitting several 10s of channels which is much longer (several meters long).
RF rotary joints can be made of copper, bronze, aluminum, stainless steel, specialty steels, silver, and specially clad or bi-metallic alloys. Important specifications for RF rotary joints include size, length and weight. Clearly, the metallic nature of RF rotary joints renders them relatively heavy.
Transferring a radio-frequency (RF) signal across the rotary joint of a rotating antenna, such as a radar antenna array, can require large and heavy RF rotary joints close to the antenna and typically high on an antenna mast, e.g. a ship's mast. This becomes a particular problem when considering antenna arrays having many RF channels, requiring a long and heavy RF rotary joint.
The invention addresses this.